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Abstract:

A resin-rubber composite in which a low pressure plasma-treated
polyamide-based resin molded product and a higher fatty acid salt-sulfur
vulcanizable acrylic rubber composition that forms an acrylic rubber
layer are directly bonded by vulcanization without interposing an
adhesive. The plasma treatment of a polyamide-based resin molded product
is performed by a low pressure plasma treatment method. When the plasma
treatment is performed by an atmospheric pressure plasma treatment
method, desired adhesion between the resin and the rubber cannot be
ensured. Here, an alkoxysilane compound in rubber composition is an
optional component, and the presence or absence of this compound does not
affect the adhesion.

Claims:

1. A resin-rubber composite in which a low pressure plasma-treated
polyamide-based resin molded product and a higher fatty acid salt-sulfur
vulcanizable acrylic rubber composition that forms an acrylic rubber
layer are directly bonded by vulcanization without interposing an
adhesive.

2. The resin-rubber composite according to claim 1, wherein the higher
fatty acid salt-sulfur vulcanizable acrylic rubber is an acrylic rubber
containing a chlorine group as a vulcanizable group.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a resin-rubber composite. More
particularly, the present invention relates to a resin-rubber composite
in which a polyamide-based resin molded product and acrylic rubber are
directly bonded without interposing an adhesive.

BACKGROUND ART

[0002] Combining polyamide-based resin molded products and acrylic rubber
into composites is generally performed by a method using an adhesive.
However, the adhesion method using an adhesive has problems not only in
that the process is complicated, requiring complicated process management
and causing high costs, but also in that it is necessary to use large
amounts of environmentally hazardous substances, such as organic
solvents.

[0003] Patent Document 1 discloses a resin-rubber laminate in which a
polyamide resin that has been subjected to plasma treatment, corona
discharge treatment, or ultraviolet irradiation treatment, and a rubber
composition to which an alkoxysilane compound of the following formula is
added:

##STR00001##

[0004] R1, R2: any functional groups

[0005]
R3, R4: hydrocarbon groups are laminated without interposing an
adhesive and bonded. However, acrylic rubber is not exemplified as a
rubber to which alkoxysilane compound is added.

[0006] Patent Document 2 discloses a method for combining a
polyamide-based resin molded product and a member comprising other
molding materials into a composite without using an adhesive, wherein at
least one of these components is treated with an openair plasma on their
contact surface prior to the production of the composite, and the other
part is then integrally molded.

[0007] Here, vulcanized rubber compounds, such as a acrylic rubber
compound, are mentioned as examples of the other molding materials;
however, such compounds are molding members (e.g., injection molding
member, extrudate, compression molding member), or semifinished products
(e.g., single- or multilayer films, textile structures, etc.), and it is
not described that the compounds are unvulcanized rubber compounds.

[0008] Moreover, Patent Document 3 discloses a fuel hose comprising a
resin layer and an outer rubber layer laminated on the outer periphery of
the resin layer, wherein after the resin layer made of a polyamide-based
resin, or the like is formed by extrusion-molding, and before the outer
rubber layer is extrusion-molded, the outer peripheral surface of the
resin layer is subjected to microwave plasma treatment under reduced
pressure. However, acrylic rubber is only exemplified as a rubber
extrusion-molding the outer rubber layer.

PRIOR ART DOCUMENTS

Patent Documents

[0009] Patent Document 1: JP-A-8-72203

[0010] Patent Document 2: JP-A-2006-205732

[0011] Patent Document 3: JP-A-2008-230244

Outline of the Invention

Problem to be Solved by the Invention

[0012] An object of the present invention is to provide a resin-rubber
composite in which a polyamide-based resin molded product and acrylic
rubber are effectively directly bonded without interposing an adhesive.

Means for Solving the Problem

[0013] Such an object of the present invention is achieved by a
resin-rubber composite in which a low pressure plasma-treated
polyamide-based resin molded product and a higher fatty acid salt-sulfur
vulcanizable acrylic rubber composition that forms an acrylic rubber
layer are directly bonded by vulcanization without interposing an
adhesive.

Effect of the Invention

[0014] The resin-rubber composite of the present invention has the
following features:

[0015] (1) The plasma treatment of a polyamide-based resin molded product
is performed by a low pressure plasma treatment method. When the plasma
treatment is performed by an atmospheric pressure plasma treatment
method, desired adhesion between the resin and the rubber cannot be
ensured.

[0016] (2) When polyphenylene sulfide, which is exemplified in Patent
Document 3, is used in place of the polyamide-based resin, no adhesion
between the resin and the acrylic rubber can be obtained.

[0017] (3) Higher fatty acid salt-sulfur vulcanizable acrylic rubber is
used as the acrylic rubber to be vulcanization-bonded to the surface of a
polyamide-based resin molded product. When acrylic rubber containing
other crosslinkable group, such as triazine vulcanizable acrylic rubber,
dithiocarbamic acid (salt) vulcanizable acrylic rubber, or organic
ammonium vulcanizable acrylic rubber, is used, a certain level of
adhesive strength is obtained in an adhesion test, described later;
however, the rubber remaining ratio is 0% in any cases.

[0018] (4) An alkoxysilane compound, which is used as an essential
component of Patent Document 1, is an optional component in the present
invention, and the presence or absence of this compound does not affect
the adhesion.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0019] Examples of the type of typical polyamides (PA) used as the
polyamide-based resin to be treated with low pressure plasma, and their
monomers are as follows:

[0020] In addition to these polyamides, PA613, 3T, PA810, PA812, PA1010,
PA1012, PA1212, PAPACM12, etc., can also be used. These polyamide-based
resins are used singly or in combination. Further, they can be used in
blending with other resins, such as polypropylene, within the range that
does not impair the object.

[0021] Furthermore, molded products of these polyamide-based resins have a
shape that allows vulcanization bonding and lamination of acrylic rubber
to obtain composites. Examples of the shape include a plate shape, a rod
shape, a hollow shape, etc., having a flat surface, a curved surface, an
irregular surface, or the like. Specific applications thereof include
hoses, anti-vibration rubber, and air springs, as well as elements of
fuel guiding systems, cooling fluid guiding systems, oil guiding systems,
and the like.

[0022] The outer surface of these polyamide-based resin molded products is
treated with low pressure plasma. Low pressure plasma treatment is
performed in a glass vacuum vessel equipped with two parallel plate
electrodes in an inert gas atmosphere of an inert gas, such as He gas, Ne
gas, Ar gas, Kr gas, Xe gas, or N2 gas, preferably He gas, Ar gas,
or N2 gas, which are used singly or in a mixture, at a pressure of
about 10 to 1,000 Pa, at an output of about 10 to 30,000 W for about 0.1
to 60 minutes, using a high frequency power source having a frequency of
40 kHz or 13.56 MHz, or a microwave power source having a frequency of
433 MHz to 2.45 GHz.

[0023] The higher fatty acid salt-sulfur vulcanizable acrylic rubber used
herein is chlorine group-containing acrylic rubber, which is an acrylic
rubber containing a chlorine group as a vulcanizable group.

[0024] Examples of the chlorine group-containing acrylic rubber include
those obtained by copolymerizing at least one of an alkyl acrylate
containing an alkyl group having 1 to 8 carbon atoms and an alkoxyalkyl
acrylate containing an alkoxyalkyl group having 2 to 8 carbon atoms, with
a chlorine group-containing unsaturated compound.

[0025] Examples of alkyl acrylates include methyl acrylate, ethyl
acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, n-hexyl
acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, and their
corresponding methacrylates. Alkyl groups having a longer chain length
are generally advantageous in terms of cold resistance, but are
disadvantageous in terms of oil resistance. Alkyl groups having a shorter
chain length show an opposite tendency. In terms of the balance between
oil resistance and cold resistance, ethyl acrylate and n-butyl acrylate
are preferably used.

[0026] Moreover, examples of alkoxyalkyl acrylates include methoxymethyl
acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, n-butoxyethyl
acrylate, ethoxypropyl acrylate, and the like; preferably 2-methoxyethyl
acrylate and 2-ethoxyethyl acrylate. Although each of such alkoxyalkyl
acrylates and alkyl acrylates may be used singly, it is preferable that
the former is used at a ratio of 60 to 0 wt. %, and that the latter is
used at a ratio of 40 to 100 wt. %. When an alkoxyalkyl acrylate is
copolymerized, oil resistance and cold resistance are well balanced.
However, when the copolymerization ratio of alkoxyalkyl acrylate is
greater than this range, normal state physical properties and heat
resistance tend to decrease.

[0027] In addition, examples of the chlorine group-containing acrylic
rubber include those in which a chlorine group-containing unsaturated
compound, such as chloroethyl vinyl ether, chloroethyl acrylate,
vinylbenzyl chloride, vinyl chloroacetate, or allyl chloroacetate, is
copolymerized at a copolymerization ratio of about 0.1 to 15 wt. %,
preferably about 0.3 to 5 wt. %, in the chlorine group-containing acrylic
rubber. Among these chlorine group-containing unsaturated compounds, when
vinyl chloroacetate, or the like, is copolymerized, active chlorine
group-containing acrylic rubber is formed.

[0029] Furthermore, in order to improve kneading processability, extrusion
processability, and other properties, a polyfunctional (meth)acrylate or
oligomer containing a glycol residue in the side chain can be further
copolymerized, if necessary. Examples thereof include di(meth)acrylates
of alkylene glycols, such as ethylene glycol, propylene glycol,
1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, and neopentyl glycol;
di(meth)acrylates of polyalkylene glycols, such as tetraethylene glycol,
tripropylene glycol, and polypropylene glycol; bisphenol Aethylene oxide
adduct diacrylate, dimethylol tricyclodecane diacrylate, glycerol
methacrylate acrylate, 3-acryloyloxyglycerol monomethacrylate, and the
like.

[0031] Examples of higher fatty acid metal salts include alkali metal
salts or alkaline earth metal salts of fatty acids containing an alkyl
group or alkenyl group having 8 to 18 carbon atoms, such as sodium
stearate, potassium stearate, potassium myristate, sodium palmitate,
calcium stearate, magnesium stearate, sodium oleate, potassium oleate,
and barium oleate. These acids are used singly or in combination at a
ratio of about 0.5 to 10 parts by weight, preferably about 1.5 to 8 parts
by weight, based on 100 parts by weight of the active chlorine
group-containing acrylic rubber.

[0032] Sulfur or a sulfur donor (e.g., high molecular weight sulfur),
which serves as a sulfur-based vulcanizing agent, is used at a ratio of
about 0.1 to 5 parts by weight, preferably about 0.3 to 3 parts by
weight, based on 100 parts by weight of the chlorine group-containing
acrylic rubber.

[0033] In addition to a higher fatty acid salt-sulfur based vulcanizing
agent, a filler, such as carbon black, silica, graphite, clay, or talc, a
plasticizer, a lubricant, a processing aid, etc., are suitably added to
the chlorine group-containing acrylic rubber, thereby forming a
composition. The composition may further contain alkoxysilane, such as
one described in Patent Document 1 above, at a ratio of about 5 parts by
weight or less, preferably about 0.05 to 1 part by weight, based on 100
parts by weight of the chlorine group-containing acrylic rubber.

[0035] A composition to which such an alkoxysilane compound is added or
not added is prepared by kneading using a closed-type kneader, roll, or
the like. The prepared composition is applied directly or as a solution,
dispersion, etc., to the surface of a polyamide-based resin molded
product, followed by vulcanization bonding under general vulcanization
conditions of acrylic rubber.

EXAMPLES

[0036] The following describes the present invention with reference to
Examples.

Example 1

[0037] A plate-like injection molded product (25×60×2 mm) made
of polyamide (PA66; Amilan CM3001-G30, produced by Toray Industries,
Inc.) was treated with low pressure plasma in a glass vacuum vessel
equipped with aluminum parallel plates under the following conditions:

[0038] Atmosphere: helium gas

[0039] Pressure: about 60 Pa

[0040]
Frequency: 40 kHz

[0041] Output: 200 W

[0042] Time: 10 minutes

[0043] A kneaded product of a higher fatty acid metal salt-sulfur
vulcanizable acrylic rubber composition of the following Formulation
Example was directly bonded, in an unvulcanized state, to one surface of
the low pressure plasma-treated polyamide plate, followed by press
vulcanization at 180° C. for 8 minutes, thereby producing a
resin-rubber composite:

[0045] The obtained resin-rubber composite was measured for the adhesive
strength and rubber-remaining area ratio by a 90-degree peel test
according to JIS K6256 (2006) corresponding to ISO 813 as adhesiveness
evaluation.

Example 2

[0046] In Example 1, as a higher fatty acid salt-sulfur vulcanizable
acrylic rubber composition, Formulation Example I that did not contain
any silane compound was used.

Examples 3 to 4

[0047] In Examples 1 to 2, a PA46 resin (Stanyl TW241F6, produced by DSM
Corporation) was used as the low pressure plasma-treated polyamide.

Comparative Example 1

[0048] In Example 2, a polyamide plate that was not treated with low
pressure plasma was used.

Comparative Example 2

[0049] In Example 2, a polyamide plate that was treated with, in place of
the low pressure plasma, atmospheric pressure plasma under the following
conditions was used:

[0050] Process gas: He

[0051] Distance between the
test piece and the plasma nozzle: 15 mm

[0052] Treating speed: 100 mm/sec

Comparative Example 3

[0053] In Example 2, a polyphenylene sulfide (Susteel PPS GS-30, produced
by Tosoh Corporation) plate that was treated in the same way with low
pressure plasma was used in place of the low pressure plasma-treated
polyamide plate.

Comparative Examples 4 to 7

[0054] In Examples 1 to 4, a triazine-vulcanizable acrylic rubber
composition of the following Formulation Example was used in place of the
higher fatty acid salt-sulfur vulcanizable acrylic rubber composition
used in Example 1:

[0056] In Examples 1 to 4, a dithiocarbamic acid vulcanizable acrylic
rubber composition of the following Formulation Example was used in place
of the higher fatty acid salt-sulfur vulcanizable acrylic rubber
composition used in Example 1:

[0058] In Examples 1 to 4, an organic ammonium vulcanizable acrylic rubber
composition of the following Formulation Example was used in place of the
higher fatty acid salt-sulfur vulcanizable acrylic rubber composition
used in Example 1:

[0060] Following Table shows the results obtained in the above Examples
and Comparative Examples, together with the kind of polyamide, kind of
plasma treatment, kind of Formulation Example and the presence or absence
of alkoxysilane.

Patent applications in class With a polycarboxylic acid or derivative and a polyamine or the corresponding salt thereof; or with a lactam; or with an aminocarboxylic acid; or with the corresponding polymers; and wherein the monomer or polymer was derived from at least one saturated reactant

Patent applications in all subclasses With a polycarboxylic acid or derivative and a polyamine or the corresponding salt thereof; or with a lactam; or with an aminocarboxylic acid; or with the corresponding polymers; and wherein the monomer or polymer was derived from at least one saturated reactant